Blade retention



Dec, 25, 1962 A. L. HUNT, JR

BLADE RETENTION v Filed Feb. e, 1959 United States Patent 3,070,351 BLADE RETENTION Albert L. Hunt, Jr., Indianapolis, Ind., assignor to General Motors CorporntiomDetroit, Mich., a corporation of Delaware Filed Feb. 6, 1959, Ser. No. 791,657 3 Claims. (Cl. 253-77) This invention relates to a blade retaining means for use in a compressor or turbine rotor assembly wherein the blades are connected to the rotor wheel by an axial interfit, and means are provided to prevent axial movement of the blades.

More specifically, this invention relates to a blade-torotor wheel connection wherein the means to prevent axial movement therebetween comprises a flexible retaining ring adapted to be snapped over a portion of the wheel into a groove therein with another portion abutting each of the blades.

Therefore, it is an object of this invention to provide a ilexible blade retaining ring to prevent relative axial movement between a blade and rotor wheel.

Other features, advantages and objects will become apparent by rreference to the detailed description of the invention and to the drawings wherein there is shown the preferred embodiment of this invention.

In the drawings:

FIGURE 1 is a front elevational perspective view of a portion of a rotor assembly embodying this invention,

FIGURE 2 is a cross-sectional view on a reduced scale 3,070,351 Patented Dec. 25, 1962 blades 14 upon rotation of the rotor tending to urge the v ceivedwithin mating dove-tail notches or grooves 32 provided in one edge of the wheel rim 22, the number of notches being equal in number to the number of depending lugs and being equally spaced around the circumference of the wheel rim 22. The radial inter-fit of each of the lugs and notches therefore prevents axial movement of the blades relative to the wheel in one direction upon rotation of the assembly. When the rotor is not turning, however, and therefore no centrifugal force is acting on the blades, some means must be provided to prevent the blades from sliding out of the notches 24 to the left as seen in FIG. 2 due to the effect of gravity on the blade and root masses.

As shown in FIGURE 2 and more specifically in FIG- URE 3, this latter means comprises a retaining ring or disc 34 having one portion 36 adapted to abut the outer face portion of the lugs 30, while another portion 38 is yieldingly secured to a portion of the wheel in a manner to be described. More specifically, rig 34 has a radially extending portion 36 with an inner portion 38 bent vinto Y an axially directed flange having a lip 40 bent in a comthrough the rotor assembly on a plane indicated by the 2, and

vFIGURE 4 is a perspective view of a detail vof FIG- URE 3.

Referring now to the drawings and more particularly to FIGURE 1, there is shown therein a portion or segment of a compressor rotor assembly 10, although the rotor may be for use in either a compressor or turbine as a matter of choice without departing from the scope of the invention. The rotor assembly includes a wheel 12 having secured thereto at its outer periphery a plurality of blades 14 by means to be described, the wheel being internally splined at 16, as seen in FIGURE 2, for driving a shaft (not shown). Wheel 12 is further provided with an axial flange 18 adapted to cooperate with a row of stator vanes (not shown), and a spline 20 adapted to mesh with a spline on the adjacent rotor wheel (not shown). The rim 22 of wheel 12 is provided with a number of transverse slots or notches 24 equally spaced around the circumference of the wheel as shown, these notches or Slots each having a dove-tail shape as seen in FIG. l for cooperation with an oppositely formed mating root portion 26 integral withk each of the blades 12. Mating of the two portions by sliding each of the roots 26 into the slots 24 locatesthe blades radially with respect to the wheel by the wedging action therebetween preventing radial separation. While the roots and notches are shown as being dove-tailed to each other, it will be clear that a fir-tree type connection or any other similar axial interft could be used without departing from the scope of the invention. A-

As shown in-FIGURES 2 and 3, the blade roots 26 and rim 22 of wheel 12 are set at an angle relative to the rotor axis simulating the angle that would be found in the first stage of a multi-stage axial flow type compressor, for example, where a ramp eect is provided to both decrease the flow area across the stage and provide the most eilicient path for the flow of air past the blading. Because of the axial interfit, and the angling of the roots and wheel rim, a centrifugal force will be exerted on the bined axial and radial direction as shown to form a hook adapted to extend into an annular groove 42 milled in the wheel. The ring is relieved or slotted at four equally spaced points 44 to permit bending of the flange 38 into the shape shown. The milling of groove 42 in the wheel provides an annular depending ridge or flange 46 adapted to cooperate with flange 38. The major portion of ilange 38 is of a dimension so that it will normally slide over the ridge 46. However, the radially outward bend of the lip provides an interference fit between the shoulder 48 of the wheel and the lip and therefore constitute an axial stop to prevent any tendency of relative axial movement between the rotor and ring.

The relief slots 44 therefore divide the flange 38 into four flexible portions which are deflected radially inwardly to ride over or clear the rib 46 upon axial movement of the ring to abut the radial portion 36 against the end of depending blade lugs 30. Therefore, as soon as lip flanges 40 have cleared rib 46, the resiliency of the lip will cause it to be snapped .back yto1its undeilected ror original shape to enter groove 42 andY thereby provide the interference fit between 'shoulder 48 and the llip preventing Y disengagement of the two parts. Thus, the blades are prescope.V of the invention The retaining ring 34 is also provided with a large number of holes 58 equally spaced around the circumference of the retaining ring and arranged radially and circumferentially so as to align some of the holes with the holes in the wheel so that the pins can be inserted therethrough or removed easily to add or change a balance weight without disassembling the wheel assembly. The surplus number of holes in the ring is merely for convenience in lining up a set of retaining ring, rotor and balance weight holes so as to reduce the assem- `bly problems in assembling the retaining ring to the rotor stages` per `se since the individual .stages generally have been balanced prior reassembly. As a rule, in an installation of the axial ow type, the rotor balance weights are attached to both the first and last stage wheels, with the `particular number of pins and balance weights being as required to balance the particular rotor assembly.

While the assembly and operation of this blade retaining means is believed to be clear from a consideration of the drawings, a brief description of the same will however be given. Initially, each of the dove-tailed blade roots `is positioned at one edge 60 of the wheel and slid axially 'through the dove-tail shaped notch 2'4 until face 62 of lug is seated against'face 64 of notch 32. The blade is thus radially positioned in both directions and axially positioned in one direction. The retaining ring 34 is then axially aligned with the wheel and abutted against the wheel:ridge 46 so that upon further axial movement of the ring, the axial ange portions 38 will be cammed or deected inwardly to permitthe lip portions 40 to ride over ridge46 and be snapped into position in the groove 42. The retaining ring 34 is thus secured to the rotor by the hooking ofthe axial ange 38 around theridge 46, `with the radialange abutting the depending lugs 30. `Each of the blades is thereforerestrained from axial movement relative to gthe rotor towards the left asseen in FIGURE 2.

The blades are therefore restrained from axial movement in the direction of the normal operating forces towards the right as seen in FIGUREZ by the abutment `of the depending lugs 30 against the face 64 of-notch 32, and in the opposite direction by the-abutment of ring 34 against the lugs. In the event. of a reversal in direction `of operating forces or other unusual occurrences wherein the application of forces is caused to befapplied against the radial flange 36 in a direction towards the left as seen `inFIGURE 2, the forces will merely cause the ring 34 to tighten in the wheel and work as a spring to resist movement of the bladestby the tighter engagement of lip portions 40 in the groove 42 and the springing of the axial flange portions 38 in a somewhat radial direction. The

'blades are thus-maintained axially from movement re- -gardless of the direction of operating forces.

Fromltheforegoing it will be seen, therefore, that this invention minimizes assembly problems by simplifying the method of retaining the blades against axial movement, whether the rotor is turning or not. Furthermore,

-contiguousradial face portions of vone side of `said rotor and portions ofall of the blade means, saidrotor having a projection adjacent said rotor radial face portion extending radially inwardly, the inner peripheral portion of said disc having a springable iingerlike clamping means extending axially from said disc and abutting said rotor projection, the axial movement of said disc and clamping means into operative position effecting the springing movement of said clamping means by said projection inwardly over the end of said projection into clamping engagement with said projection to securely fasten said disc and rotor together preventing axial sliding movement of said blade means past said disc.

2. A rotor assembly including a rotor, a plurality of .blade means extending radially outwardly of and secured to said rotorfor a substantially axial slidable movement therebetween, and retaining means preventing said movement, said retaining means including a at washer-like disc in operative position located at against substantially contiguous radial face portions of one side of said rotor and portions of all of the blade means, said rotor having a projection adjacent said rotor radial face portion extending radially inwardly, the inner peripheral portion of said disc having a springable fingerlike ange extending axially from said disc and abutting said rotor projection, the edge of said ange having a hook shape in cross section, the axial movement of said disc `and tlange into operative position effecting the springing movement of saidange by said projection inwardly over the end of `said projection -interengaging the hook shaped edge of `said-flange and said V.projection securely fastening said disc and rotor together preventing axial sliding movement of said blade means past said disc.

3. A rotor assembly including a rotor, a plurality of blade means extending radiallyoutwardly of and secured to'saidrotor for-a substantially axial slidable movement therebetween, and retaining means preventing said movement, said retaining means including a flat washer-like disc in operative` position locatedzat against` substantially contiguous radial face portions 0f one side of said rotor and portions of` all of the blade means, said rotor having a projection adjacent said rotor radial face portion extend- `ing radiallyinwardly, the inner peripheral portion of said Ldisc-having-` an annular flange-like clamping `means extending axially from said disc and abutting said rotor projection,said clamping means comprising a plurality of circumferentially arranged and separated springable arcuate clamping portions, the axial movement of said disc Vandflange-like meansginto operative position effecting the springing movement of ,said clamping portions by said projection inwardly over the end of said projection into clamping engagement with said projection to securely .fasten saididisc and rotortogether preventing axial sliding movement of said blademeans past said disc.

Refererences Cited in the file of this patent UNITED STATES PATENTS 

